This invention relates to vehicle headlamps. The Applicant's U.S. Ser. No. 3,849,642 issued on Nov. 19, 1974 to Olivier PUYPLAT relates to a motor vehicle headlamp comprising a parabolic mirror, a lamp having a dipped beam filament disposed in front of the focus of the mirror, the mirror having a central part immediately surrounding the lamp and a peripheral part surrounding the central part, a front lens provided whith relief patterns to intercept and disperse at least a part of the reflected dipped beam, and an auxiliary lens positioned between the lamp and the front lens and provided with relief patterns to intercept and disperse at least that part of the dipped beam which is reflected by the central part of the parabolic mirror.
It is disclosed in the U.S. patent referred to above that the front lens and the auxiliary lens are both rigidly connected to the mirror or to the mirror support so as to form an optical unit which can be introduced into a vehicle body.
The proposed function of the front lens of the system described above is to engage closely with the shape of the vehicle body so as to prevent a break of styling lines such as would occur if conventional headlamps were used since a break of this kind is bound to impair the aesthetics and streamlining of the body. However, in the case of body shapes which are very inclined to the headlamp optical axis, the optical system embodied by the front lens, auxiliary lens and mirror tends to become of substantial size and weight so that it is difficult to secure or mount the unit on the body. The problems are even greater if it is desired to introduce mechanism for compensating the horizontal inclination of the reflector axis in dependence inter alia on vehicle attitude since compensation of this kind leads to considerable movement of the optical system. Also the bulk and weight of the optical system causes difficulties in the construction of compensating systems since these must allow for the inertia and considerable overhang of the unit and the weight of the front lens and of the air pressure acting thereon.